Porting to OS/2: Case #14 open() and DASD access

On Unix-like systems, open() can open various devices including files, storages and so on. On OS/2 kLIBC as well, open() does like that. However, open() of kLIBC does not support DASD. If you open [x:] expecting to open a drive x: in DASD mode, your expectation will go wrong. Although open() for x: succeeds, it is not for DASD mode, but for a directory. The handle returned can be used with functions which do not alter a file position and contents. For examples, fchdir() and fstat().

Then what is how to open in DASD mode ? Use a wrapper function for DosOpen(). The following are the codes used by libdvdnav. 

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#ifdef __OS2__ #define INCL_DOS #include <os2safe.h> #include <os2.h> #include <io.h>     /* setmode() */ #include <fcntl.h>  /* O_BINARY  */ #endif #ifdef __OS2__ #define open os2_open static int os2_open(const char *name, int oflag) {   HFILE hfile;   ULONG ulAction;   ULONG rc;   rc = DosOpenL(name, &hfile, &ulAction, 0, FILE_NORMAL,                 OPEN_ACTION_OPEN_IF_EXISTS | OPEN_ACTION_FAIL_IF_NEW,                 OPEN_ACCESS_READONLY | OPEN_SHARE_DENYNONE | OPEN_FLAGS_DASD,                 NULL);   if(rc)     return -1;   setmode(hfile, O_BINARY);   return (int)hfile; } #endif

Note that all open()s after the above codes try to open in DASD mode. If opening a normal file or a directory is necessary, undefine open.